The present invention relates to an actuator device with a processing unit for use in a motor vehicle, which comprises a main control device. The processing unit is subordinate to the main control device.
“Intelligent” actuators are frequently used in modern motor vehicles. They usually incorporate a processing unit which is subordinate to a main control device, which in turn transmits control commands, for example actuator setting commands, to the processing unit. The processing unit receives the control commands from the main control device and is provided to control the actuator according to the commands transmitted from the main control device. This main control device operates as a master unit and the processing unit functions as the slave unit. Such a concept is described, for example, in the document WO 2006/061238, and corresponding US patent No. 2008/105502 A1, the US document being incorporated by reference herein, and enables power electronics for activating the actuator to be arranged so that it is spatially separate from the main control device. The communication between the main control device and the processing unit normally takes place via a data bus. In motor vehicles, such a bus is frequently a LIN bus, a CAN bus or a FlexRay bus.
Intelligent actuators of this type may be used in motor vehicles in particular for safety-related systems such as electronically controllable parking brake systems. Problems may occur, however, if incorrect signals are transmitted via the bus or if the actuator receives, for example via a short circuit, erroneous signals. If safety-related systems are affected by a fault of this kind, there could be serious consequences for the vehicle safety. For example, in the case of a parking brake, an incorrect signal may cause the parking brake to be released without control on a slope, or may lead to unexpected and undesired braking while the vehicle is travelling. Both situations may significantly prejudice the safety of the driver and passengers of a motor vehicle and that of other road users.
A safety concept that counteracts faults of this kind can usually only be implemented at great expense. The need therefore exists for a simple, cost-effective yet reliable system for increasing vehicle safety.